Microorganisms of the Methane Cycle in Copepods from a High-Altitude Lake

The microbiome of copepods of the genus Diaptomus from a high-altitude lake at Western Caucasus was investigated using 16S rRNA gene profiling. Aerobic and anaerobic organotrophic microorganisms, methanogenic archaea, and aerobic methane-oxidizing bacteria (MOB) constituted the basis of the microbiome. The symbionts and bacteria of the copepod diet were revealed. Anaerobic organotrophic microorganisms inhabiting the copepods provide the substrates for methanogens, the second most abundant physiological group of prokaryotes in the microbiome. Acetoclastic methanogens of the genus Methanothrix and hydrogenotrophic methanogens of the genera Methanobacterium and Methanoregula were predominant. The methane cycle within the copepods was closed, since their microbiome contained a diverse population of aerobic MOB, among which members of the genera Methylobacter and Methyloparacoccus (class Gammaproteobacteria) predominated. Methane exchange between methanogens and methanotrophs occurs probably in the anoxic environment of the copepod intestine under direct contact of the target microorganisms.